Designing Ion‐Selective Membranes for Vanadium Redox Flow Batteries

Abstract

With the increase in the world's population and industrialization, world energy consumption experienced an ascending trend in the last years, [1] which is anticipated to continue in the future. As such, the sustainable supply of energy is critical, relying on both renewable and unrenewable sources. However, an essential aspect in this context is that generally, the rates of generation and consumption of energy do not coincide with each other because of the need for peak shaving or load leveling in power grids or due to the intermittent nature of such ever-developing renewable sources like solar or wind energies. Accordingly, to overcome such temporal mismatches, the adaptation of efficient and reliable timeshifting technologies, i.e., energy storage systems (ESSs), must be pursued. Such solutions also make it possible to develop distributed energy generation technologies as well as increase efficiency. Among various developed or emerging ESSs, [2,3] electrochemical batteries show longer discharge time at the rated power (energy) in larger-scale power system. [4] Redox flow batteries (RFBs) are a well-known type of electrochemical rechargeable batteries. Anodic and/or cathodic redox-active materials are commonly dissolved in their respective electrolyte and flow from external reservoirs on electrodes where they undergo redox reactions during charge/discharge processes. These batteries have shown some advantages such as rapid response time, flexible installation, easy modularization, scalability, and short construction cycles, were made them suitable candidates for large-scale electrical energy storage purposes. [7] Among all various RFBs, Vanadium redox flow batteries (VRFBs) are the most widely studied, promising, and wellestablished technology due to their attractive characteristics for large-scale ESS. The idea of using vanadium redox couples goes back to 1933 and 1954 when two patents of P.A Pissoort (France) and Walter Kango (Germany) were established. [8] However, the first VRFBs were developed in the 1980s by the Skyllas-Kazacos group. Since then, the history of VRFBs is significantly tied with different efforts for the development of other flow or redox flow-based batteries, as schematically presented in Figure 1a. Motivated by promising as well as proven merits, different VRFBs demonstrations with the scale from tens of kW to MW have been successfully tested, and it is believed that the It is predicted that the future of energy will mainly rely on batteries such as vanadium redox flow batteries (VRFBs), and its related research has already attracted significant attention. The primary function of a membrane in VRFBs is to control proton transport between the half-cells and to hinder admixing the anolyte and catholyte at the same time. However, to develop a low-cost and energy-efficient VRFB, other membrane roles are crucial. The combination of a highly stable backbone of polytetrafluoroethylene with hydrophilic perfluorinated-vinyl-polyether side chains equipped with sulfonic acid groups (Nafion membranes)...

Comprehensive Analysis of Critical Issues in All-Vanadium Redox Flow Battery

“…The membrane accounts for a significant ratio of the total cost of the system, and the performance of the battery is significant. To solve these challenges, the current studies of membranes are mainly concentrated on high-performance membranes with high electrical conductivities, low permeabilities, chemical properties, and stable mechanical properties . To sum up, the ideal ion exchange membrane should have the performance characteristics as shown in Figure .…”

“…To solve these challenges, the current studies of membranes are mainly concentrated on high-performance membranes with high electrical conductivities, low permeabilities, chemical properties, and stable mechanical properties. 82 To sum up, the ideal ion exchange membrane should have the performance characteristics as shown in Figure 8. 83 In addition, the availability of raw materials, operability, and rationality of the membrane-making process are the key factors for the commercial use of VRFB ionic conductive membranes, and also important aspects to be considered in the future development of VRFB ionic conductive membranes.…”

Functionalized Metallic 2D Transition Metal Dichalcogenide-Based Solid-State Electrolyte for Flexible All-Solid-State Supercapacitors

“…Compared to gel ones, SPEs typically show superior dimensional stability and mechanical strength. , Examples of SPEs are proton-conducting polymers, such as Nafion (brand name for sulfonated tetrafluoroethylene based fluoropolymer-copolymer) and sulfonated poly­(ether ether ketone) (SPEEK), , which are also widely exploited in the form of proton-exchange membranes (PEMs) for several energy storage and conversion applications. , Despite its high proton conductivity (σ, around 90 mS cm –1 at 25 °C) and its satisfactory mechanical and thermal stabilities, , Nafion has a high cost (∼$200 USD, 30 × 30 cm –2 for Nafion 117) that may limit its application in practical FSSSCs, whose market uptake is still at its infancy. Alternatively, SPEEK is a hydrocarbon-based thermoplastic polymer with mechanical strength (tensile strength ∼37 MPa, i.e., 80% higher than Nafion 117), thermal stability (up to 300 °C), , commercial availability of the polymeric precursor (i.e., poly­(ether ether ketone) -PEEK-), and σ (up to 40 mS cm –1 at 25 °C) adequate for the massive development of solid-state electrolytes for FSSSCs. , Furthermore, SPEEK has been extensively established as PEM material for fuel cells, − electrolyzers, , and redox-flow batteries. − Importantly, the physical/electrical/(electro)­chemical properties of SPEEK, including σ, water uptake (WU), and membrane swelling (MS), are determined by its degree of sulfonation (DS). , More in detail, the presence of acidic functional groups, i.e., −HSO 3 – , attached to the hydrophobic backbone of the polymer, form hydrophilic domains that have ion transferring capabilities . Although σ increases with increasing DS, excessive sulfonation deteriorates the mechanical strength of SPEEK.…”

“… 54 , 63 Furthermore, SPEEK has been extensively established as PEM material for fuel cells, 64 − 66 electrolyzers, 67 , 68 and redox-flow batteries. 69 − 72 Importantly, the physical/electrical/(electro)chemical properties of SPEEK, including σ, water uptake (WU), and membrane swelling (MS), are determined by its degree of sulfonation (DS). 73 , 74 More in detail, the presence of acidic functional groups, i.e., −HSO 3 – , attached to the hydrophobic backbone of the polymer, form hydrophilic domains that have ion transferring capabilities.…”

Study on the Self-Discharge of an All-Vanadium Redox Flow Battery through Monitoring Individual Cell Voltages

“…Moreover, improved ion exchange membrane selectivity to vanadium ions and protons has resulted in improved battery performance. Amiri and Thiam described the importance of membrane selectivity and its influence on battery performance. In addition to a suitable electrode and membrane, an electrode modified with a electrocatalyst can considerably enhance the battery performance.…”